Abstract
Dating of shallow groundwater: Comparison of the transient tracers 3H/3He, chlorofluorocarbons, and 85Kr
Department of Geological Sciences, Columbia University, New York
Department of Geological Sciences, Columbia University, New York
Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York
U.S. Geological Survey, Reston, Virginia
U.S. Geological Survey, Reston, Virginia
U.S. Geological Survey, Reston, Virginia
Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York
Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York
This paper describes a direct comparison of apparent ages derived from 3H/3He, chlorofluorocarbons (CCl3F and CCl2F2), and 85Kr measurements in shallow groundwater. Wells chosen for this study are completed in the unconfined surficial aquifers in late Cenozoic Atlantic Coastal Plain sediments of the Delmarva Peninsula, on the east coast of the United States. Most of the apparent tracer ages agree within 2 years of each other for recharge dates between 1965 and 1990. Discrepancies in apparent tracer ages usually can be explained by hydrological processes such as mixing in a discharge area. Recharge rate calculations based on apparent tracer age gradients at multilevel well locations agree with previous recharge estimates. High recharge rates on the Delmarva Peninsula result in nearly complete dissolved-gas confinement in the groundwater. The remarkable agreement between the different tracer ages indicates negligible mixing of waters of different ages, insignificant dispersion, minimal gas loss to the atmosphere, and insignificant sorption-desorption processes at this location.
Received 12 April 1993; accepted 17 January 1994; .
Citation: (1994), Dating of shallow groundwater: Comparison of the transient tracers 3H/3He, chlorofluorocarbons, and 85Kr, Water Resour. Res., 30(6), 1693–1708.
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